llafro

I have a 2004 GTO LS1 with a Magnacharger M112 kit installed on it. The kit has been on the car for going on 10 years now and about 70,000 miles. For the last couple of years, I have noticed some knock that is audible under high load. The problem was that my wife was in law school, so there was not really any money for anything except that, so I just had to daily drive the car and not really beat on it. It's not that hard to do in the end. :-)

I have logged it with a wireless OBD dongle and my phone. The knock shows up as 2-4 degrees. It seems to come in at low RPM / high load situations (for example, rolling into the throttle from 2,000 RPM in 4th gear). Once the car gets above 3-4 lbs boost, I start hearing knock and it shows up on the scanner. I also hear it on full throttle runs higher up in the RPM range.

This week, I finally got HP Tuners in order to look at what's going on in the tune. It seems like the Magnacharger canned tune that has been in the car from the time I installed the blower has a fairly low entry point to PE mode. Both the cold and hot PE tables show 18% as the threshold across the board for entry into PE mode. The Power Enrich EQ table shows that it should be commanding approximately 12.9 AFR at 1200 RPM to 10.8 AFR at 6,000 RPM (PE Eq ratios from 1.130 to 1.350). I think the somewhat rich high RPM data is to compensate for the stock fuel system that isn't boost referenced. Otherwise, how would it account for the drop in fuel delivery as boost increases?

I have replaced the stock fuel pump with a Deatschwerks 265 lph drop-in pump. The fuel pressure stays right at 58 on the gauge I have mounted in the dash pod (the stock pump tended to drop 5-10 psi under the same conditions). The change in fuel pump didn't improve the knock behavior.

I am in California, and we are stuck with 91 octane with 10% ethanol. There is no option for 93 here.

Am I right in that the way the car is configured, it will go into PE mode at anything other than light throttle? If so, the place to adjust for AFR would be in the PE table, right? I can also pull some timing from the overall table to see if that helps.

I have a wideband O2 sensor/controller that I need to wire into the PCM, so that's really the next step. But any advice so far?

1FastBrick

iTrader: (16)

Just an FYI the gas in CA has gotten so bad, I usually see more like 15% ethanol. They have removed most of the the stickers from pumps that used to say "May contain up to 10% ethanol"

Dragls

All this talk about afr, what's does your timing curve look like?

Ambient temperature?

Spark plug heat range?

llafro

Timing tables from HP Tuners:
High Octane


Low Octane (seems to be the same as the High Octane one)


Plugs are NGK TR6 gapped at 0.035

Ambient temperatures don't seem to matter that much. It was pinging last night with outside temps of 50-60 degrees.

llafro

So, if the fuel is 15% ethanol, that makes the stoichiometric ratio more like 13.7:1 for that particular fuel blend. That much may be beyond the adaptation routines in the PCM. It's effectively lean by a almost full point.

I wonder if I set the stoichiometric ratio in the tune to 13:7 instead if that might not solve the problem. Just spitballing...

1FastBrick

iTrader: (16)

Yeah, was trying to figure out why my flex fuel truck was commanding so much fuel. Then we looked at the ethanol content % and it clicked. Around that time I noticed they were starting to remove the labels on the pumps.

TPIZ92

iTrader: (10)

What are the logs showing for spark? Look at the air temp modifiers as well. What are the intake temps doing and are they removing spark accordingly? I found that the stock air temp modifiers do a pretty good/accurate job of removing the necessary spark advance. What do the long and short terms look like on a log? If they are adding a ton of fuel, changing the stoich might be a good idea. If you are regularly filling up at a particular station, I would actually test the fuel too. See what the ethanol content actually is.

ddnspider

iTrader: (26)

Easiest way to see if it's real is pull the same 2 to 4 degrees that you're seeing of knock counts and make a pull. If they go away it's real knock and if it's still 2 to 4 then it's false. Seeing that you said it's audible it sounds real and you just have too much timing vs leaner AFR vs crap gas.

Longblue

My friend has a magnacharger on his Silverado and had a similar issue recently that went on for a while with knock showing up and audible pinging. He found that the pump for the intercooler had quit and no coolant was circulating causing high IAT's. Replaced pump and knock/pinging went away.

llafro

I regularly check the intercooler pump when I check the oil. It's easy to turn the key on and hear the water flowing in the reservoir on top of the battery. I know the pump is working because I just went out and double checked it.

In looking at a log I did of driving home and blasting up the on-ramp a bit, I see the following:

4461 RPM / 47% throttle / 27 degrees total timing, 27.4 base advance / 77.8 kPa Maf / LTFT of 8.5 and 10.7 / engine temp. 205 / IAT 111 (outside temps in the mid 60s)

The PE table shows it going into PE mode at anything above 30% throttle, regardless of RPM.

There are lots of places in the log where the LTFT figures are between 12 and 14%. It's looking like it's going lean a lot of the time. The numbers seem to ramp up under throttle. They peak after decel and then start dropping again.

I will try to get a few good pulls logged over the next couple of days to help see what's going on. Too much turkey to eat this weekend!

pdxmotorhead

I haven't seen the document in a long time, but the percentage of AL in the fuel was supposed to go up 5% every other year if I recall, so this year was 15%, 2020 is 20%.. It was Buried in some bill during the Obama years.. Part of the 50MPG average stuff.. Never mind that our current import percent of oil is like 6%.. so we are importing ethanol instead of oil..

llafro

I loaded up the scanner this morning and tried to do some pulls on the freeway on the way to work this morning. Outside temps were in the mid 60s.

Here is a graph during a 60-100 pull in fourth gear:



As you can see, there is a good chunk of knock when it goes full throttle. It maxes out around 2.8*. I am also attaching the whole log of about 10 minutes. The first thing in there is a run up the onramp at full throttle. I had to get out of it, since I was catching up HARD to the car that turned before me. Even though I let it get most of the way up the onramp, the Magnacharger just wanted to eat that Honda Civic... :-)

Now I just need to get the wideband installed, so I can really see what's going on.

dw456post

You need to log cylinder airmass so you can tell where you are on the timing chart. Post up your tune, that would be a help. And yes, get a wideband. 2.8 degrees is not so bad but stock pistons do not like knock and lean at the same time. And make your low octane table 4 degrees lower than the high octane table for safety.

llafro

I had included the cylinder airmass in the log, so it was easy to create a new graph. I also added the base advance to the graph with the total advance and knock retard. The MAF figures are now in g/s instead of lbs, because OCD. The tune is attached. This is Magancharger's canned tune that came with the kit I bought in 2008.

dw456post

It's knocking at 3200rpm and .72g in the chart which is 20 degrees. Reduce the timing 1 degree on the .72g row from 2800rpm to the end of the row, smooth it out. If you want to be safe, do the row above also, same cells. The other little blip can be done the same way if it is there constantly. Your VE table needs a little work--smoothing --and the upper rpm end shouldn't drop off like that. I know the wot part is extended, but the other part is just lazy.

dw456post

Be sure and save your tune somewhere before you go changing it.

LilJayV10

iTrader: (39)

Has burst knock been disabled?

When it starts knocking, with only 17 degrees of timing, Kpa is only 105. However if you are still running a 1 bar MAP or haven't selected the right MAP sensor to log it's going to show 105kpa when you are in boost regardless.

The way it's pulling timing out on the hit looks like burst knock to me but that doesn't explain your audible knock unless you have a crap load of oil in the intake...that will do it too.

LilJayV10

iTrader: (39)

Can you post a log and tune? That will help a lot.

llafro

The MAP sensor is the stock 1-bar unit. Magnacharger's kit doesn't use a 2-bar sensor or tune. I did create a version of the tune with a 2-bar OS just to see what the difference is.

I pulled off both PCV lines to the intake, and there wasn't any visible oil in them. I know the LS2 GTOs had more of an issue with oil consumption through the PCV. My LS1 has always been solid in that respect. I am tempted, though, to pull the blower off and disassemble it to see how gunked up it is. The blower has gone almost 80,000 miles on the car. It can't hurt to clean it up.

Both the tune and the log that generated the graphs I posted are linked above.

LilJayV10

iTrader: (39)

I see them now, sorry I missed them the first time